CN1216192C - A method for preparing carbon fibers and carbon nanotubes - Google Patents

Abstract

The present invention relates to a carbon fiber/a nanometer carbon tube, and concretely relates to a method for preparing the carbon fiber and the nanometer carbon tube. In the present invention, hydrogen is used as a carrier gas; acetylene is used as a carbon source, and foam nickel is used as a catalyst; when the carbon source is added, a growth promoter containing sulfur is also added; the two substances react at low temperature, and then, the nanometer carbon tube, the nanometer carbon fiber or the spiral carbon fiber is prepared. The present invention has the advantages of simple technology, low price and high yield and purity, is applied to structure enhanced materials, microelectronic devices, wave absorption materials, etc., and has wide application prospect.

Description

A method for preparing carbon fibers and carbon nanotubes

technical field

The invention relates to carbon fiber/carbon nanotube, in particular to a method for preparing carbon fiber and carbon nanotube.

Background technique

Carbon fiber/carbon nanotubes have excellent properties such as high specific modulus, high specific strength, and high conductivity, and are expected to be used in catalysts and catalyst supports, lithium-ion secondary battery anode materials, electric double-layer electrical electrodes, high-efficiency adsorbents, and separation agents , Structural reinforcement materials, etc. At present, carbon fibers and carbon nanotubes are generally prepared by chemical vapor deposition (CVD), using low-carbon hydrocarbon compounds as raw materials, hydrogen as a carrier, Fe, Co, Ni and their alloys as catalysts, and carbon fibers can be prepared at 873K ~ 1473K / carbon nanotubes. Specifically, it can be divided into substrate method, spray method and floating catalyst method. The so-called matrix method is to use graphite or ceramics as the matrix, use nano-scale catalyst particles as "seeds", pass hydrocarbon gas compounds under high temperature, decompose and precipitate carbon fibers on the catalyst side. Although this method can produce high-quality products, the catalyst is sprayed unevenly on the substrate, and the yield is not high because the carbon fibers only grow on the substrate with the catalyst. It is generally believed that the inner diameter of carbon fibers and carbon nanotubes is equal to the diameter of catalyst particles, and people always try to obtain catalysts with smaller particle sizes, but the preparation of small-diameter catalysts is difficult and expensive, and its application is limited to a certain extent.

The spraying method provides the possibility of preparing a large number of carbon nanofibers, but because the ratio of hydrocarbons and catalysts is difficult to optimize, the catalyst distribution is not uniform during the spraying process, and the sprayed catalyst particles are difficult to exist in the form of nanometers, so in the preparation of fibers The process is accompanied by a large amount of carbon black formation.

For the floating catalyst method, the metallic organic matter containing catalysis is generally volatilized at a certain temperature, enters the high-temperature reaction zone in gaseous form, is decomposed by heat, and produces metal particles with catalytic effect, and the carbon generated by the decomposition of the organic matter is deposited on the metal surface to grow into a carbon nanofiber. The metal particles produced by this method are easy to aggregate into large metal particles when they collide with each other in the gaseous state, so the parameters of preparing carbon nanofibers/carbon nanotubes are difficult to control and the operation is relatively complicated.

Contents of the invention

The purpose of the present invention is to provide a method for preparing carbon nanotubes and carbon fibers with relatively simple operation, high output and low cost.

In order to achieve the above object, the technical scheme of the present invention is: adopt hydrogen as carrier gas, acetylene as carbon source, nickel foam (without pulverization) as catalyst, add sulfur-containing growth accelerator while adding carbon source, Under the following reaction, carbon nanotubes, carbon nanofibers or helical carbon fibers (including single and double helical carbon fibers) are prepared; wherein: the ratio of hydrogen to acetylene flow rate is 3 to 5:1; the addition of sulfur-containing growth promoter is 0.3 to 1mol%; the diameter and shape of the product are mainly controlled by adjusting process parameters such as flow rate and temperature;

The sulfur-containing growth promoter is thiophene or hydrogen sulfide, which is used to effectively increase its yield; before the reaction, soak the foamed nickel in 5-10% dilute acid for 1-10 hours, and use it after drying.

Compared with the carbon fiber/carbon nanotubes prepared by the traditional CVD method, the catalyst requirements are high, the process is complicated, and the cost is high, the present invention has the following beneficial effects:

1. The process is simple and the price is low. The present invention is a new method which is different from both the matrix method and the floating catalyst method. It proposes to use nickel foam as a catalyst, which can reduce costs, and uses hydrogen as a carrier gas, acetylene as a carbon source, and adds a The sulfur growth accelerator can prepare a large amount of relatively pure carbon nanotubes and carbon fibers at a relatively low temperature (such as 873K-1173K), with convenient operation and simple process.

2. High output. The present invention adopts nickel foam as a catalyst, hydrogen as a carrier gas and adding a small amount of sulfur-containing accelerator can efficiently and easily prepare carbon fibers and carbon nanotubes on a large scale while reducing costs, and the high yield (up to more than 600%) is extremely A new preparation method with industrial application potential. Electron microscope analysis showed that the product was of high purity. The performance (mechanics, electricity, etc.) of carbon nanotubes and carbon fibers can also be tested conveniently by using this material.

3. It has broad application prospects. The invention can be applied to structural reinforcement, microelectronic devices, wave-absorbing materials and the like.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the device used in the preparation of carbon nanotubes and carbon fibers in the present invention.

Fig. 2a is a scanning electron micrograph of the carbon fiber of Example 1 of the present invention.

Fig. 2b is a transmission electron micrograph of a carbon tube in Example 1 of the present invention.

Fig. 3a is a transmission electron micrograph of the single helical carbon fiber of Example 2 of the present invention.

Fig. 3b is a scanning electron micrograph of another single helical carbon fiber in Example 2 of the present invention.

Fig. 4a is a transmission electron micrograph of the single helical carbon fiber of Example 3 of the present invention.

Fig. 4b is a transmission electron micrograph of another single helical carbon fiber in Example 3 of the present invention.

Fig. 5a is a scanning electron micrograph of the double helix carbon fiber of Example 4 of the present invention.

Fig. 5b is a scanning electron micrograph of another double helix carbon fiber in Example 4 of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

Example 1

As shown in Figure 1, the used device of the present invention is made up of hydrogen tank 1, acetylene tank 2, flowmeter 3, temperature controller 4, reaction furnace 5, is controlled the temperature of reaction furnace 5 by temperature controller 4, passes through hydrogen tank 1, The acetylene tank 2 adds hydrogen or acetylene into the reaction furnace 5, and its flow rate is controlled by the flow meter 3; the reaction furnace 5 in this embodiment adopts a tube furnace.

Before reaction, 0.574g foamed nickel is placed on the constant temperature zone of tube furnace, under hydrogen atmosphere, reaction is warmed up to 953K, feeds acetylene and adds sulfur-containing growth accelerator thiophene simultaneously, and add-on is (0.6mol%), hydrogen and The ratio of acetylene flow rate is 3.7:1 (wherein: acetylene is 75ml/min, hydrogen is 277.5ml/min), reaction constant temperature time is 60min, carries out pyrolysis reaction; Natural cooling to room temperature after reaction finishes. 3.4456 g of carbon nanofibers (see FIG. 2a ) and carbon nanotubes (see FIG. 2b ) can be obtained, with a yield of 600%.

Example 2

The difference from Example 1 is:

Soak the nickel foam in 10% dilute hydrochloric acid for 1 hour before the reaction, place 0.593g of nickel foam in the constant temperature zone of the tube furnace after drying, raise the reaction temperature to 973K under a hydrogen atmosphere, feed acetylene, and add sulfur-containing growth promoter at the same time Agent thiophene (add-on is 0.5mol%), the ratio of hydrogen and acetylene flow is 4: 1 (wherein: acetylene is 58ml/min, and hydrogen is 232ml/min). The reaction constant temperature time was 45min, and the reaction was naturally cooled to room temperature after completion of the reaction. 2.5451 g of single helical carbon fibers can be obtained (see FIG. 3 a, FIG. 3 b ), with a yield of 429%.

Example 3

The difference from Example 1 is:

Soak the nickel foam in 5% dilute hydrochloric acid for 6 hours before the reaction, place 0.425g of nickel foam in the constant temperature zone of the tube furnace after drying, raise the temperature of the reaction to 993K under a hydrogen atmosphere, feed acetylene, and add sulfur-containing growth promoter at the same time Agent thiophene (add-on is 0.9mol%), the ratio of hydrogen and acetylene flow is 4.5: 1 (wherein: acetylene is 65ml/min, and hydrogen is 292.5ml/min). The reaction constant temperature time is 35min. After the reaction was completed, it was naturally cooled to room temperature. 0.8523g of single helical carbon fiber can be obtained (see Fig. 4a, Fig. 4b), and the yield is 200%.

Example 4

The difference from Example 1 is:

Soak the nickel foam in 8% dilute hydrochloric acid for 2 hours before the reaction, place 0.376g of nickel foam in the constant temperature zone of the tube furnace after drying, raise the reaction temperature to 1023K under a hydrogen atmosphere, feed acetylene, and add sulfur-containing growth promoter at the same time Agent thiophene (add-on is 0.75mol%), the ratio of hydrogen and acetylene flow is 4.2: 1 (wherein: acetylene is 60ml/min, and hydrogen is 252ml/min). The reaction constant temperature time is 30min. After the reaction was completed, it was naturally cooled to room temperature. 0.9455 g of double helix carbon fibers can be obtained (see Fig. 5a, Fig. 5b). Yield 251%.

The sulfur-containing growth promoter of the present invention can also use hydrogen sulfide.

Claims (4)

1. method for preparing carbon fiber and CNT (carbon nano-tube), it is characterized in that: employing hydrogen is that carrier gas, acetylene are that carbon source, nickel foam are catalyst, when adding carbon source, add and contain growth promoter of sulfur, under 873K～1173K temperature, react, prepare CNT (carbon nano-tube), carbon nano-fiber or helical carbon fiber.

2. according to the described method for preparing carbon fiber and CNT (carbon nano-tube) of claim 1, it is characterized in that: described hydrogen is 3～5: 1 with the ratio of acetylene flow.

3. according to the described method for preparing carbon fiber and CNT (carbon nano-tube) of claim 1, it is characterized in that: the described growth promoter of sulfur that contains is thiophene phenol or hydrogen sulfide, and its addition is 0.3～1mol%.

4. according to the described method for preparing carbon fiber and CNT (carbon nano-tube) of claim 1, it is characterized in that: before reaction described nickel foam was soaked in 5～10% diluted acid 1～10 hour, use dry back.

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